The inspection of nuclear test locales is one manner of inspection mechanism for CTBT, which includes the technical means such as seismic surveillance, radionuclide detection, sonar and infrasonic detection. In which, radionuclide detection may be the most effective and reliable inspection means at present. The gaseous radionuclides that are detectable within quite a period after nuclear explosion mainly include 37Ar, 131,131mXe, 133,133mXe, 135Xe, 85Kr, T and etc. Xe has high isotopic activity and detection sensitivity, but with short half-life and short duration for detection. 85Kr and T have too long half-life, and it is impossible to judge whether they are resulted from a new nuclear test, which thus are not suitable for inspection in country having nuclear source. 37Ar, as a characteristic neutron activation product resulted from underground nuclear explosion, is featured with moderate half-life, low natural background and etc., which can be effectively detected within a period of 60 days or more after nuclear explosion. 37Ar gas generated from underground nuclear test leaks upward the ground through soil fissures (cracks), which is diluted and forms a concentration gradient from the underground to the ground. Nevertheless, the content of 37Ar is still very low in the soil gas, and its radioactivity cannot be detected by directly measuring a soil gas sample in the inspection. Instead, 37Ar must be firstly separated from the soil gas sample following by purifying and concentrating to obtain a source for measuring radioactivity, and then the radioactivity is measured by using a measuring equipment of nuclear physics. At present, there isn't a set of 37Ar measuring system suitable for locales inspection in the world. In china, no appropriate method for separating, purifying and measuring 37Ar from a soil gas and an atmospheric sample has ever been established. A method for measuring low-activity 37Ar has ever been reported only in Switzerland (Dr. Hugo Loosli, 37Ar is an Excellent Tool to Detect Subsurface Nuclear Explosions. CTBT/OSI/WS-10/PR/24, 2004.10.20), namely, a method using similar measuring equipment and energy spectrum measuring, wherein the background was reduced to less than 0.1 mBq by means of exterior and interior lead shielding, the measuring time of one sample was a week, and the minimum detection concentration might attain to less than 0.1 mBq/L Ar. However, this method is in need of many conditions that cannot be satisfied in locales inspection.